A blood oxygen sensing device includes a sensor, a processing module and a display module. The sensor emits first and second sensing light sources to a to-be-sensed target alternately, and generate first and second sensing signals. The processing module generates first and second sensing signal base lines, generates a heartbeat pulse signal according to the first and second sensing signals matching a first preset range, records a pulse amplitude signal and a DC signal of the heartbeat pulse signal matching a second preset range, and generates a blood oxygen value and a pulse value according to the pulse amplitude signal and the DC signal. The processing module chronologically sorts the blood oxygen values and the pulse values in a sequential order, respectively. The display module is connected to the processing module and receives and displays the blood oxygen value and the pulse value updated.
